Hardwood flooring over particle board underlayment

This is a remodel, and after pulling up the carpet, where I plan to install the Bamboo, I find 1/2" particle board underlayment on top of 3/4" OSB. My understanding is that nailing directly on to 3/4" OSB is acceptable. Is that 1/2" layer of particle board really such a problem that I need to remove it?

Would not the staples grab the OSB anyway, and negate the poor holding power of the particle board?

Is particle board so suseptible to moisture damage that liquid spills on such an assembly would cause major problems?

It is O.K. to install the bamboo over the partical board underlayment - if moisture is your only concern, then simply lay down a vapor barrier prior to installing the bamboo and keep the finished floor as dry as possible. There is one question you should be asking yourself, and that is: "If I install 3/4" bamboo over the underlayment, what kind of floor height problems may occur?" Remember, you are raising the finished floor height. You typically can find this to be an issue if you are installing the floor into the kitchen area, where you can "lock-in" an appliance such as a dishwasher, or the refrigerator may not fit into the opening anymore. The other area where this can be of issue is at exterior doors (the finished floor may be higher than the threshhold).